Description
Measure signed days from a drug study's supplied index date.
Medication-study records distinguish supplied coverage intervals, observed person-days, dispensing reversals and source event definitions. Inclusive calendar-day counting differs from continuous elapsed time. Recorded supply and washout flags are study conventions rather than evidence of ingestion, drug clearance, causal effect or suitable treatment.
Measure signed days from a drug study's supplied index date.
When to use this tool
Use Drug Study Index Date Offset when you already have indexDate, observationDate and need to measure signed days from a drug study's supplied index date.
How to use the tool and how it works
- Enter indexDate, observationDate. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read signedCalendarDays. Use the output convention below.
Parse real UTC dates; return observationDate-indexDate in calendar days.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| indexDate | Index Date | Required. Text; maximum UTF-16 length 8192. Real proleptic Gregorian YYYY-MM-DD; four-digit years 0000-9999 accepted. |
| observationDate | Observation Date | Required. Text; maximum UTF-16 length 8192. Real proleptic Gregorian YYYY-MM-DD; four-digit years 0000-9999 accepted. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| signedCalendarDays | Signed Calendar Days | Required. Finite number. |
{
"input": {
"indexDate": "2026-10-28",
"observationDate": "2026-11-01"
},
"output": {
"signedCalendarDays": 4
}
}Limitations and assumptions
- A negative offset is retained; no valid study index, exposure assignment, treatment or causal interpretation is selected.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Alternative or Complementary methods
Construct exposure episodes from a documented study rule and verified dispensing or observation history. Keep inclusive calendar coverage distinct from elapsed time and actual ingestion; evaluate causal questions with a complete study design rather than one interval flag.
References
Similar or alternative tools
- Drug Study Person Day Contribution
Count inclusive person-days inside two supplied calendar intervals.
- Prescription Coverage End Date
Calculate an inclusive supply end date from supplied start and day count.